PC Physx Patch released 20 Dec 2013
One article here
Here
Adds physx to smoke, smoke particles now have physx (physics) implemented, they linker for longer, cast shadows, are effected by weather, wind and turbulence along with being effected by NPCs characters and obstacles passing through them,
The particles now stack which means the more canons you fire on a ship the thicker the smoke, and the same for pistols, this makes naval combats feel so much more information intence because after a single broadside you can no longer see your enemies
Also turbulence has been added, its not as good as what we have seen in watchdogs but it is very similar to the turbulence we have seen in batman arkham origins,
This update may majena tiny difference to most casual gamers but even on low quality settings it makes a very big difference to the overall atmosphere
Strangely enough ubisoft have not announced (via ubibkog) any details obout this update
Update
And the ofifical nVidia article about this
Can be found here
This is nVidia's update, as far as I can tell, all these changes are programmed and made by nVidia and NOT ubisoft, that is why it is PC only